1. Field of the Invention
The present invention relates to a method of manufacturing a thin film magnetic head and, more particularly, a thin film magnetic head wherein a magnetoresistive device is covered with an insulating nonmagnetic layer such as alumina and a pattern of a magnetic layer (shielding layer) is formed on the insulating nonmagnetic layer using a photolithography technique and a method of manufacturing the same and a magnetic memory apparatus including the same therein.
2. Description of the Prior Art
With the demand for high recording density of the magnetic memory apparatus in a computer, the thin film magnetic head has been used in recent years. The thin film magnetic head of this kind has been manufactured in virtue of photolithography technique. There are two types of thin film magnetic head; one is that read and write operations are performed by an inductive head (a head being made up of a core and coils) respectively, and the other is that a write operation is performed by the inductive head while a read operation is performed by the magnetoresistance head (MR head) including the magnetoresistive device (MR device). The magnetoresistive device has advantageous features that it has excellent magnetic sensitivity and that it can cope well with high recording density.
For the purposes of example, the conventional thin film magnetic head including the magnetoresistive device is composed as shown in FIG. 1. The magnetic head consists of an AlTiC substrate 21; an alumina (Al.sub.2 O.sub.3) layer 22, a lower shielding layer 23 and an alumina layer 24, which being stacked sequentially on the substrate 21 from the bottom; a SAL (Soft Adjacent Layer) 25a, a nonmagnetic layer 25b, and a magnetoresistance layer (referred to as an "MR layer" hereinafter) 25c, which constituting the magnetoresistive device 25 and being formed in sequence on the alumina layer 24; a pair of terminals 26 connected respectively to both ends of the magnetoresistive device 25; an alumina layer 27 for covering the magnetoresistive device 25 and the terminals 26; and an upper shielding layer 30 formed on the alumina layer 27 and in a region directly over the magnetoresistive device 25.
FIGS. 2A to 2C are sectional views showing a method of manufacturing the above conventional thin film magnetic head in order of the manufacturing steps.
First, as shown in FIG. 2A, the alumina layer 22 is formed on the AlTiC substrate 21 using a sputtering technique or ion beam sputtering technique, and the lower shielding layer 23 made up of magnetic metal is then formed on the alumina layer 22.
Then, the alumina layer 24 is formed on the lower shielding layer 23 using a sputtering technique or ion beam sputtering technique. Subsequently, the SAL 25a, the nonmagnetic layer 25b, and the MR layer 25c are formed on the alumina layer 24 in order. The magnetoresistive device 25 may then be finished by patterning these three layers 25a, 25b, 25c as a rectangular shape if they are viewed from the upper direction. Next, a metal film is formed all over the surface, and the terminals 26 are then formed on both end portions of the magnetoresistive device 25 by patterning the metal film. Thereafter, the alumina layer 27 is formed on the entirety of the resultant structure so as to cover the magnetoresistive device 25 and the terminals 26.
Next, as shown in FIG. 2B, a photoresist film 29 is formed on the alumina layer 27 using a spin coating technique. The photoresist film 29 located in a region of the alumina layer 27 just over the magnetoresistive device 25 is then removed via exposure and developing processes to thus form an opening 29a.
Then, as shown in FIG. 2C, a magnetic metal film 30a is formed all over surfaces of the resultant structure. The photoresist film 29 and the magnetic metal film 30a thereon are then removed so only the magnetic metal film 30a remains in a region over the magnetoresistive device 25. The remaining portion of the magnetic metal film 30a serves as the upper shielding layer 30. The thin film magnetic head shown in FIG. 1 has been derived in a fashion as described above.
Usually, a novolac resin containing a phenol is used as the principal ingredient of the photoresist, and a potassium hydroxide, a sodium hydroxide or a tetramethyl hydroxide is used as the principal ingredient of a liquid developer for the photoresist.
However, according to the foregoing conventional method of manufacturing the thin film magnetic head, the alumina layer 27 would be corroded by liquid developer when the pattern of the photoresist film is formed on the alumina layer 27. As a result, either a film thickness of the alumina layer 27 would be lessened or pin holes would be caused in the alumina layer 27. Therefore, insulation resistance and breakdown voltage performance of the alumina layer 27 would be in some cases deteriorated. In addition, magnetic anisotropy of the upper shielding layer 30 formed on the alumina layer 27 would become unstable because of deterioration in the surface state of the alumina layer 27 due to liquid developer. This would sometimes result in reduction in the magnetic characteristic of the alumina layer 27.
For this reason, there has been proposed in Patent Application Publication (KOKAI) 6-203326 that, in manufacturing steps of the inductive head, the alumina layer which is difficult to be eroded by alkali liquid developer should be formed by supplying a large bias electric power to the substrate when the alumina layer constituting the head gap is formed in virtue of bias sputtering technique. But it would be obvious that this alumina layer cannot prevent sufficiently reduction in the film thickness of the alumina layer and deterioration in the breakdown voltage performance thereof due to the liquid developer.